Pedicle Screw Fixation Assemblies with Sawtooth Locking
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Solution Overview
Problem
Current bone stabilization assemblies in spinal implants face challenges in securely fixing pedicle screws to vertebrae, as existing systems may not adequately prevent relative movement between the screw and the bone, leading to potential instability and loosening over time.
Innovation Solution
The proposed solution involves a bone stabilizer assembly with a coupling member and compression nut that engage via locking portions, limiting relative rotation without deflecting the threaded surfaces, and a saddle mechanism that compresses the screw head against a seat, ensuring secure fixation and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a compression nut is used to secure the pedicle screw to the vertebrae, then the fixation strength is improved, but relative movement between the screw and coupling element may still occur leading to loosening over time
Solution Approach 1:
The locking member incorporates asymmetric features including a sawtooth profile with inclined locking surfaces and a detent mechanism with asymmetric engagement geometry. The sawtooth edges have inclined surfaces that allow easy insertion but prevent reverse movement, creating a one-way locking action that maintains fixation strength and prevents loosening over time.
Solution Approach 2:
The locking member is pre-configured with deflected locking surfaces that are biased toward the locked position. The spring-loaded detent mechanism is pre-loaded to automatically engage with the corresponding feature on the compression nut, ensuring that the anti-rotation locking action is established before any loosening can occur.
2Force
If the locking member deflects the threaded internal surfaces to engage the compression nut, then the compression force is improved, but relative rotation between the coupling member and compression nut is not limited
Solution Approach 1:
The locking member integrates two distinct functions into a single component: (1) a compression function achieved by deflecting the threaded internal surfaces of the coupling member to generate radial outward force on the compression nut, and (2) an anti-rotation function achieved through sawtooth edges and detent mechanisms that limit relative rotation between the coupling member and compression nut.
Solution Approach 2:
The locking member serves multiple purposes simultaneously: it applies compression force to secure the pedicle screw, prevents relative rotation between components, and maintains the structural integrity of the fixation assembly. This multi-functional design eliminates the need for separate compression and locking mechanisms.
3Stability of the object's composition
If the locking member features sawtooth edges to limit relative rotation, then the anti-rotation capability is improved, but the manufacturing complexity increases
Solution Approach 1:
The sawtooth edges are implemented only in the specific regions where anti-rotation locking is required, rather than throughout the entire locking member. The deflected threaded internal surfaces maintain a standard cylindrical geometry for easy manufacturing, while only localized portions feature the asymmetric sawtooth profile and detent geometry needed for rotation limitation.
Data Source
AI summary
An orthopedic device has a configuration that employs a scalloped profile that defines internal scalloped edges having troughs and crests that extend substantially along the outer edge of a head of the device. The troughs and crests interface with a series of troughs and crests around the openings in the device. Each of the openings includes an outwardly extending slot that permits the opening to expand and contract outward as the head of the anchor is rotated. This enables an anti-backout feature that prevents or substantially inhibits undesired rotation and backout.